Defibrillator with implantable medical device detection

ABSTRACT

In general, the invention is directed to techniques for using an external defibrillator to detect a presence of an implantable medical device (IMD) implanted within a patient, and providing therapy to the patient through communication between the external defibrillator and the IMD. An external defibrillator provides prompts to a user of the external defibrillator to determine the presence of an IMD implanted within the patient. For example, the external defibrillator may prompt the user to visually inspect the patient&#39;s chest for signs that an IMD was implanted, such as a scar or raised portion of skin near the patient&#39;s clavicles. As another example, the external defibrillator may prompt the user to place a detection device on the patient&#39;s chest. The detection device may be coupled to the external defibrillator, and may employ a magnet to initiate telemetry by the IMD to detect the presence of the IMD.

This application is a Divisional of U.S. patent application Ser. No.11/316,198, filed Dec. 22, 2005, the entire content of which isincorporated herein by reference.

TECHNICAL FIELD

The invention relates to emergency medical devices and, moreparticularly, to external defibrillators.

BACKGROUND

An external defibrillator delivers energy to a heart of a patient viaelectrodes placed upon the patient's chest. External defibrillators areused to deliver energy in the form of a defibrillation shock to a heartthat is undergoing ventricular fibrillation and has lost its ability tocontract. Ventricular fibrillation is particularly life threateningbecause activity within the ventricles of the heart is so uncoordinatedthat virtually no pumping of blood takes place. If untreated, a patientsuffering from fibrillation may die within a matter of minutes.

An electric shock delivered to a fibrillating heart may depolarize theheart and cause it to reestablish a normal sinus rhythm. In some cases,the patient may need multiple shocks, and the external defibrillator maydeliver different quantities of energy with each defibrillation shock.Further, the defibrillator may provide additional or alternativetherapies to the patient, such as cardioversion or pacing therapy. Asexamples, the external defibrillator may be an automated externaldefibrillator (AED) used by a first responder or bystander to treat thepatient, or a more fully-featured defibrillator/monitor used byparamedics.

SUMMARY

In general, the invention is directed to an external defibrillatorequipped to aid a user in detecting the presence of an implantablemedical device (IMD) within a patient. Upon detection of an IMD, theexternal defibrillator may communicate with the IMD to obtain usefulinformation or coordinate delivery of therapy to the patient. Asexamples, the external defibrillator may receive patient or therapyinformation from the IMD, prompt a user based on information receivedfrom the IMD, deliver therapy based on information received from theIMD, control delivery of therapy by the IMD, and store informationwithin the IMD. Alternatively, or additionally, detection of IMDlocation may permit the user to place defibrillation electrodes in alocation which will reduce the chance of damage to the IMD while stillproviding effective defibrillation therapy to the patient.

The external defibrillator may provide prompts to guide a user of theexternal defibrillator in detecting the presence of an IMD implantedwithin the patient. For example, the external defibrillator may promptthe user to visually inspect the patient's chest for signs that an IMDwas implanted, such as a scar or raised portion of skin near thepatient's clavicles. As another example, the external defibrillator mayprompt the user to place a detection device on the patient's chest. Thedetection device may be coupled to the external defibrillator, and mayemploy a detector to locate an IMD. When an IMD is detected, theexternal defibrillator or detection device may emit a notification. Forexample, the detection device may have an audible or visual indicatorthat assists the user in positioning the detection device.

The external defibrillator may obtain information from a detected IMD orcoordinate delivery of therapy with the IMD by wireless telemetry. Forexample, the detection device may be integrated with wireless telemetrycircuitry to facilitate communication with the IMD. In some embodiments,the detection device may include an adhesive interface to permitadhesive fixation of the detection device at the IMD location, therebypromoting more reliable telemetry. The external defibrillator maydeliver therapy based on information received from the IMD in thepatient. The external defibrillator may select an energy level for adefibrillation shock to be delivered to the patient based on an energylevel of a defibrillation shock previously delivered to the patient bythe IMD. As another example, the external defibrillator may analyze anelectrogram (EGM) or electrocardiogram (ECG), or output received fromthe IMD indicating pace, shock or sense events, to determine whether todeliver a defibrillation shock to the patient.

In one embodiment, the invention provides an external defibrillatorcomprising a defibrillation therapy generator, electrodes coupled to thedefibrillation therapy generator, and a user interface that presents oneor more prompts to a user of the external defibrillator to detectpresence of an implantable medical device (IMD) in a patient.

In another embodiment, the invention provides a method comprisinggenerating one or more prompts to a user of an external defibrillator todetect presence of an implantable medical device (IMD) in a patient.

In an additional embodiment, the invention provides an externaldefibrillator comprising a defibrillation therapy generator, electrodescoupled to the defibrillation therapy generator, and a detection devicethat detects presence of an implantable medical device (IMD) in apatient.

In another embodiment, the invention provides a method comprisingdetecting presence of an implantable medical device (IMD) in a patientvia a detection device associated with an external defibrillator, andindicating presence of the IMD to a user of the external defibrillator.

In various embodiments, the invention may provide one or moreadvantages. For example, prompts delivered by an external defibrillatormay permit a user to more readily detect the presence and location of anIMD. Upon detection of the IMD location, a user can place defibrillationelectrodes at a location which will reduce the chance of damage to theIMD while still providing effective defibrillation therapy to thepatient. In addition, a detection device may facilitate rapid detectionof the IMD, which promotes timely delivery of therapy. With the abilityto communicate with a detected IMD, an external defibrillator mayprovide more effective treatment to a patient in which the IMD isimplanted, permitting coordinated delivery of therapy. In addition, bycommunication with the IMD, the external defibrillator may moreeffectively obtain and manage medical information such as patientinformation or therapy information.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram illustrating an external defibrillatorproviding a user prompt for locating an IMD implanted within a patient.

FIG. 2 is a conceptual diagram illustrating an external defibrillatorproviding a second user prompt for locating an IMD implanted within apatient.

FIG. 3 is a conceptual diagram illustrating an external defibrillatorproviding a third user prompt for locating an IMD implanted within apatient.

FIG. 4 is a conceptual diagram illustrating an external defibrillatorproviding a user prompt for placing defibrillation electrodes on apatient.

FIG. 5 is a block diagram illustrating example components of theexternal defibrillator of FIG. 1.

FIG. 6 is a flowchart illustrating exemplary operation of an externaldefibrillator.

FIG. 7 is a block diagram illustrating example components of an IMDdetection device for use with the external defibrillator of FIG. 1.

FIG. 8 is a block diagram illustrating an example IMD detection devicethat includes an adhesive layer and a removable backing layer.

FIG. 9 is a conceptual diagram illustrating an example system thatincludes an external defibrillator communicating with an IMD implantedwithin a patient.

DETAILED DESCRIPTION

FIG. 1 is a conceptual diagram illustrating an example system 10 thatincludes an external defibrillator 12 providing a user prompt 34 forlocating an implantable medical device 14 implanted within a patient 16.External defibrillator 12 may be brought to patient 16 in response to amedical emergency involving patient 16, such as a ventricularfibrillation (VF) or sudden cardiac arrest (SCA) experienced by thepatient. External defibrillator 12 may be, for example, an automatedexternal defibrillator (AED), or a more fully featured externaldefibrillator/monitor, such as those used by paramedics or other medicalprofessional. However, the generation of user prompts may be especiallyuseful to a user of an AED. An AED provides basic life support (BLS)services. A more fully featured external defibrillator/monitor mayprovide advanced life support (ALS) services.

In the illustrated example, external defibrillator 12 is coupled to twoelectrodes 18A and 18B (collectively “electrodes 18”) that are appliedto the skin of patient 16. Electrodes 18 may be electrodes pads, whichmay include an adhesive backing for attachment to the skin of patient16, as is known in the art. Electrodes 18 are coupled to defibrillator12 by respective leads or cables 20A and 20B (collectively “cables 20”).Although illustrated in FIG. 1 as coupled to two electrodes 18, externaldefibrillator 12 may be coupled to any number of electrodes 18, whichmay be incorporated into common electrode pads, and may share commoncables 20. External defibrillator 12 may additionally include one ormore sensors (not shown in FIG. 1), such as blood oxygen saturation ornoninvasive blood pressure sensors.

External defibrillator 12 detects electrical activity of the heart 22 ofpatient 16 via electrodes 18, and delivers electrical stimulation toheart 22 via electrodes 18. For example, defibrillator 12 may deliverone or more defibrillation shocks to patient 16 via electrodes 18. Asshown in FIG. 1, defibrillator 12 may include a display 24, and mayprovide instructions in the form of visual prompts and other informationto a user via the display. External defibrillator 12 may, for example,display an electrocardiogram generated based on the electrical activitydetected by electrodes 18 via display 24. In some embodiments, asmentioned above, defibrillator 12 may be coupled to additional sensorsfor sensing other physiological parameters of patient 16, such as bloodpressure and oxygen saturation, and may display current or averagevalues for the additional parameters via display 24. Externaldefibrillator 12 may also include a speaker 32 to provide audible userprompts.

In the illustrated example, IMD 14 is a multi-chamber cardiac pacemakercoupled to leads 26A-26C (collectively “leads 26”) that extend toselected positions within heart 22, such as the right atrium, rightventricle, and left ventricle. As an alternative or in addition topacing pulses, IMD 14 may deliver cardioversion and/or defibrillationshocks to heart 22 via leads 26. Hence, IMD 14 may be an implantablecardioverter-defibrillator (ICD), as is known in the art. Further, IMD14 may sense electrical activity of heart 22 via leads 26.

Leads 26 may include any of a variety of types of electrodes (not shown)known in the art for use in sensing cardiac electrical activity anddelivering these types of stimulation to heart 22. The number andpositions of leads 26 depicted in FIG. 1 are merely exemplary. Further,the invention is not limited to systems 10 in which an IMD is apacemaker. IMD 14 may be any type of IMD that senses one or morephysiological parameters of patient 16 and/or delivers one or moretherapies to the patient. For example, IMD 14 may be an implantableneurostimulator, muscle stimulator, gastrointestinal stimulator, animplantable pump, or an implantable monitor such as an implantable looprecorder.

In the example of FIG. 1, external defibrillator 12 provides a userprompt 34 to aid a user in locating an IMD implanted within patient 16.User prompt 34 may be an audible prompt provided via speaker 32.Alternatively, user prompt 34 may be a visual prompt such as a textprompt, pictorial prompt, or other visual prompt. In some embodiments,defibrillator 12 may provide both audible and visual prompts. Externaldefibrillator 12 may prompt the user to visually inspect an area of thepatient's body, e.g., the patient's chest or abdomen for signs that anIMD was implanted in patient 16. Where the patient is a child, an IMDmay be implanted in the patient's abdomen. User prompt 34 prompts a userto look for a scar near the patient's clavicle, i.e., collarbone. Such ascar may indicate the presence of an IMD implanted within patient 16.Visual and audible prompts may originate from external defibrillator 12or from a detection device 28, as will be described, in order tofacilitate optimal positioning of the detection device over the patient.

External defibrillator 12 may include a user interface that provides amedium for user input indicating whether the user has found a scar nearthe patient's clavicle. As one example, display 24 may includeinteractive touchscreen displays in which the user may push a buttonshown on display 24 to indicate responses to user prompts. Otherinterface media such as buttons, switches, hardkeys and softkeys may beused. Such interface media may additionally or alternatively be locatedon detection device 28. In the case that the user indicates he or shehas found a scar near the patient's clavicle, external defibrillator 12may provide follow-up prompts instructing the user to place detectiondevice 28 on the patient's chest near the scar, so that detection device28 may establish communication with IMD 14, as described in furtherdetail below.

In some embodiments, external defibrillator 12 is capable ofcommunicating with IMD 14 by wireless telemetry. External defibrillator12 communicates with IMD 14 via telemetry circuitry similar to that usedby dedicated programming devices to communicate with the IMD. Dedicatedprogramming devices may communicate with IMD 14 via its telemetrycircuitry to program or reprogram the operating parameters of the IMD,or to retrieve information stored or collected by the IMD, as is knownin the art. Like dedicated programming devices, external defibrillator12 may include corresponding telemetry circuitry to facilitatecommunication with IMD 14 via its telemetry circuitry. The telemetrycircuitry of external defibrillator 12 and IMD 14 may include suitabletransceivers, magnets and antennas for communication via radio-frequency(RF) telemetry.

In the example illustrated by FIG. 1, external defibrillator 12 iscoupled to detection device 28 by cable 30. Cable 30 may includeconductors to carry both power and data to and from detection device 28.Alternatively, in some embodiments, detection device 28 may bebattery-powered and communicate with external defibrillator 12 bywireless telemetry. Detection device 28 is placed proximate to, e.g.,over, IMD 14 by a user of defibrillator 12 to enable the externaldefibrillator 12 to detect and optionally communicate with the IMD. Inaddition to detecting the presence of IMD 14 in patient 16, thedetection device 28 may identify or indicate a location of IMD 14 withinthe patient. In some embodiments, detection device 28 also includes atelemetry device having an antenna and magnet, enabling defibrillator 12to communicate with the IMD. Defibrillator 12 may be removably orpermanently coupled to detection device 28 by cable 30. In someembodiments, detection device 28 may be integral with a housing ofexternal defibrillator 12, or incorporated into one of electrodes 18 andcoupled to the external defibrillator by a lead 20. In otherembodiments, detection device 28 may not be coupled to defibrillator 12via cable 30, but may instead communicate with defibrillator 12 viawireless communication, such as RF or infrared communication.

Detection device 28 may include a magnet to open or close a switchwithin IMD 14 and thereby initiate telemetry by the IMD. In particular,by swiping detection device 28 across the patient's body near asuspected implant site, the detection device triggers wireless telemetryby IMD 14. Telemetry circuitry within detection device 28 then maycommunicate with IMD 14 and/or measure signal strength of telemetrysignals transmitted by IMD 14 to guide the user to place the detectiondevice over the implant site of the IMD. Visual and auditory prompts toguide placement of detection device 28 to a position in proximity to theimplant site may originate from the detection device 28 or externaldefibrillator 12.

For example, detection device 28 may include a visual indicator such asa series of lights. As detection device 28 approaches the implant siteof IMD 14, a greater number of lights are activated, thereby guidingplacement of the detection device toward the implant site.Alternatively, or additionally, an audible indicator may be provided bydetection device 28 or defibrillator 12. For example, the audibleindicator may be a speaker that emits an audible beep or pitch thatincreases in volume or frequency as the detection device 28 approachesthe implant site, or speech output much like the prompts describedabove. The speaker may be provided in detection device 28 ordefibrillator 12. In each case, the output of the visual or audibleindicator is a function of the measured signal strength of the telemetrysignals emitted by IMD 14.

In another embodiment, detection device 28 detects the presence of IMD14 by inducing IMD 14 to initiate a specific pacing protocol when themagnet is positioned near IMD 14. The frequency and duration of thepacing may be measured by external defibrillator 12 via electrodes 18.Magnet rate profiles are different for different pacemaker anddefibrillator manufacturers. The change in pacing rate from before andafter detection device 28 was applied would be interpreted by externaldefibrillator 12 as an IMD. This information may allow externaldefibrillator 12 to confirm when pacing was occurring and determinewhether the patient was in ventricular fibrillation and in need oftherapy

In some embodiments, the telemetry circuitry and antennae of externaldefibrillator 12 and IMD 14 may be configured to support a signalstrength, other signal characteristics, and communication protocol thatallow RF telemetry communication between the external defibrillator andthe IMD at relatively greater distances. In such embodiments, one ormore antennae of external defibrillator 12 may be housed within thedefibrillator. In this case, external defibrillator 12 need not becoupled to detection device 28 to communicate with the IMD, anddefibrillator 12 may detect and communicate with IMD when brought intogeneral proximity with the IMD.

FIG. 2 is a conceptual diagram illustrating external defibrillator 12 inthe course of providing another user prompt 40 to aid a user in locatingan IMD 14 implanted within a patient 16. Again, user prompt 40 may be avoice prompt provided via speaker 32, a visual prompt provided bydisplay 24, or a combination of both. In the example of FIG. 2, prompt40 advises the user to visually inspect the patient's chest for othersigns that an IMD has been implanted in patient 16. In particular, userprompt 34 prompts a user to look for a raised portion of the skin nearpatient's collarbone. Such a raised portion of the skin may indicate thepresence of an IMD implanted within patient 16.

Prompt 40 may be provided if the user is unable to identify a scar perprompt 34 of FIG. 1. Alternatively, prompt 40 may be provided even ifthe user identifies a scar in order to aid the user in more preciselyidentifying the position of IMD 14, which may not be located immediatelyunder the scar. In the case that the user indicates he has found a scarnear the patient's clavicle, or found a raised portion of the skin nearthe patient's collarbone, external defibrillator 12 may providefollow-up voice prompts instructing the user to place detection device28 on the patient's chest near the scar, so that detection device 28 mayverify the presence of IMD 14 and/or establish communication with IMD 14via telemetry circuitry contained in detection device 28.

External defibrillator 12 may provide other voice prompts to guide theuser in determining whether an IMD is implanted within patient 16. Forexample, external defibrillator 12 may prompt the user to make a tactilesearch for an IMD by palpitating the patient's chest at an area near thepatient's clavicles to feel for an IMD. In other words, the usermanipulates the tissue near the clavicles for tactile detection of theIMD, which should feel like a hard object embedded within the tissue. Asone example, tactile detection may be done when the patient's size orweight is such that an IMD is not readily visually detectable.

FIG. 3 is a conceptual diagram illustrating external defibrillator 12 inthe course of providing another user prompt 44 for locating animplantable medical device 14 implanted within a patient 16. As oneexample, where a user has been prompted according to FIGS. 1 and 2, buthas been unable to visually locate evidence of an IMD in patient 16,external defibrillator 12 may prompt the user via user prompt 44 toplace the detection device 28 near an area of the patient's body, e.g.,the patient's chest near the patient's clavicle, or the patient'sabdomen where the patient is a child.

Detection device 28 may use a magnetic, metal-detecting feature todetect an IMD implanted within patient 16 in a manner similar to aconventional magnetic stud finder. Alternatively, detection device 28may use another detection method such as an acoustically-based detectionmethod. Consequently, when the user places detection device 28 on thepatient's chest near a clavicle, detection device 28 may detect thepresence of an IMD implanted within patient 16.

Detection device 28 may contain an output medium that indicates to theuser that the detection device has located an IMD, such as LED lights,beeping, text alerts, or other indication means. As another example,display 24 of external defibrillator 12 may display a message indicatingthat detection device 28 has located an IMD. External defibrillator 12may display a pictorial indication of a location of IMD 14 withinpatient 16. Further, detection device 28 may include telemetry circuitryfor communicating with IMD 14. In this embodiment, externaldefibrillator 12 may display a message to indicate that externaldefibrillator 12 has established communication with IMD 14.

FIG. 4 is a conceptual diagram illustrating an example system 10 thatincludes an external defibrillator 12 providing a user prompt 48 forplacing electrodes 18 of the external defibrillator 12 on a patient 16.As illustrated in FIG. 4, detection device 28 has been placed on thechest of patient 16, and is in communication with IMD 14. It may beundesirable for external defibrillator electrodes to be placed directlyover IMD 14, because energy from electrodes 18 may electrically damageIMD 14. Consequently, external defibrillator 12 prompts a user via userprompt 48 to place the electrodes on the patient's chest, away from thelocation of the IMD 14. By placing electrodes 18 at locations somedistance from the implant location of IMD 14, interference betweenexternal defibrillator 12 and IMD 14 may be reduced. Interferencebetween external defibrillator 12 and IMD 14 may include electromagneticinterference, which may degrade the signals generated by sensors of IMD14 and sensors of external defibrillator 12.

FIG. 5 is a block diagram further illustrating exemplary components ofexternal defibrillator 12. In FIG. 5, external defibrillator 12 is showncoupled to patient 16 by electrodes 18 and corresponding cables 20, asdescribed above. In a typical application, therapy interface 60 ofexternal defibrillator 12 includes a receptacle, and cables 20 plug intothe receptacle.

Therapy interface 60 includes a switch (not shown in FIG. 5) that, whenactivated, couples an energy storage circuit 62 to electrodes 18. Energystorage circuit 62 stores energy to be delivered to patient 16 in theform of a defibrillation shock. The switch may be of conventional designand may be formed, for example, of electrically operated relays.Alternatively, the switch may comprise an arrangement of solid-statedevices such as silicon-controlled rectifiers or insulated gate bipolartransistors.

Energy storage circuit 62 includes components, such as one or morecapacitors, that store the energy to be delivered to patient 16 viaelectrodes 18. Before a defibrillation shock may be delivered to patient16, energy storage circuit 62 must be charged. A processor 64 directs acharging circuit 66 to charge energy storage circuit 62 to a highvoltage level. Charging circuit 66 comprises, for example, a flybackcharger that transfers energy from a power source 68 to energy storagecircuit 62.

As indicated above, external defibrillator 12 may be a manualdefibrillator or an AED. Where external defibrillator 12 is a manualdefibrillator, a user of defibrillator 12 may select an energy level foreach defibrillation shock delivered to patient 16. Processor 64 mayreceive the selection made by the user via a user interface 70, whichmay include input devices, such as a keypad and various buttons ordials, and output devices, such as various indicator lights, display 24(FIG. 1), and a speaker. Display 24 may include a cathode ray tube(CRT), light emitting diode (LED) array, plasma screen, or liquidcrystal display (LCD) screen.

Where external defibrillator 12 is an AED, processor 64 selects anenergy level. For example, processor 64 may select an energy level froma preprogrammed progression of energy levels stored in a memory 72 basedon the number of defibrillation shocks already delivered to patient 16.In some manual defibrillator embodiments, processor 64 may select anenergy level, e.g., based on a preprogrammed progression, to recommendto a user via user interface 70.

In either case, when the energy stored in energy storage circuit 62reaches the desired energy level, processor 64 controls user interface70 to provide an indication to the user that external defibrillator 12is ready to deliver a defibrillation shock to patient 16. For example,the indication may be an indicator light or other visual or audibleprompt. The defibrillation shock may be delivered manually orautomatically. Where the defibrillation shock is delivered manually, theuser may direct processor 64 to deliver the defibrillation shock viauser interface 70 by, for example, pressing a button. In either case,processor 64 activates the switches of interface 60 to electricallyconnect energy storage circuit 62 to electrodes 18, and thereby deliverthe defibrillation shock to patient 16. Therapy interface 60, energystorage circuitry 62 and charging circuit 66 are examples of therapydelivery circuitry that deliver therapy to patient 16 under control ofprocessor 64.

Processor 64 or other circuitry modulates the defibrillation shockwaveform delivered to patient 16. Processor 64 may, for example, controlthe switches of interface 60 to regulate the shape and width of theshock. Processor 64 may control the switches to modulate the shock to,for example, provide a multiphasic shock, such as a biphasic truncatedexponential shock, as is known in the art.

Processor 64 may perform other functions as well, such as monitoringelectrical activity of the heart of patient 16 sensed via electrodes 18.Therapy interface 60 may include circuitry for sensing the electricalactivity of the heart via electrodes 18. Processor 64 determines whetherheart 22 of patient 16 is fibrillating based upon the sensed electricalactivity in order to determine whether a defibrillation shock should bedelivered to patient 16. Where a defibrillation shock has already beendelivered, processor 64 evaluates the efficacy of the delivereddefibrillation shock by determining if heart 22 is still fibrillating inorder to determine whether an additional defibrillation shock iswarranted. Processor 64 may automatically deliver defibrillation shocksbased on these determinations, or may advise the caregiver of thesedeterminations via user interface 70. Processor 64 may display anelectrocardiogram (ECG) that reflects the sensed electrical activity viauser interface 70, e.g., via display 24 (FIG. 1).

Processor 64 may store an indication of the time of delivery of eachdefibrillation shock delivered to patient 16 as medical eventinformation within memory 72 for patient 16. Processor 64 may also storethe energy level of each pulse and other characteristics of each pulse,such as the width, amplitude, or shape, as medical event information forpatient 16. Processor 64 may also store a digital representation of theECG, or a heart rate over time determined based on the electricalactivity of the heart of patient 16 detected via electrodes 18 withinmemory 72 as medical event information for patient 16. Further,processor 64 may control delivery of other types of therapy to patient16 via electrodes 18, such as cardioversion or pacing therapy, and storeinformation describing the times that such therapies were delivered andparameters of such therapies, such as cardioversion pulse energy levelsand pacing rates, as medical event information for patient 16.

Where external defibrillator 12 is more fully featured, e.g., a manualparamedic or hospital defibrillator, defibrillator 12 may also includeadditional sensors 74A-74N (collectively “sensors 74”) coupled toprocessor 64, such as sensors to measure blood oxygen saturation, bloodpressure, respiration, and the amount of oxygen or carbon dioxide in theair inhaled or exhaled by patient 16. Sensors 74 may be included withinor coupled to external defibrillator 12. External defibrillator 12 mayinclude circuitry that conditions the signals generated by sensors 74such that they may be analyzed by processor 64, such as one or moreanalog to digital converters to, and suitable filter and amplifiercircuitry.

Processor 64 may also store the signals generated by these sensorswithin memory 72 as medical event information for patient 16. Asexamples, processor 64 may store any of a capnograph, a plethysmograph,a blood oxygen saturation over time, a blood pressure over time, a pulserate over time determined based on measured blood pressure, end tidalcarbon dioxide measurements, and/or measurements of the fraction ofcarbon dioxide in air inspired or expired within memory 72 as medicalevent information for patient 16. Processor 64 may also receive otherinformation collected by a user during treatment of patient 16, such asa location of treatment or time of death, and store such information asmedical event information for the patient. Processor 64 may begin tostore medical event information in memory 72 when defibrillator 12 ispowered on to respond to a medical emergency involving patient 16.

Processor 64 may, for example, include one or more of a microprocessor,DSP, ASIC, FPGA, or other equivalent integrated or discrete logiccircuitry. Memory 72 may include program instructions that causeprocessor 64 to perform the functions attributed to processor 64 anddefibrillator 12 herein. Accordingly, this disclosure also contemplatescomputer-readable media storing instructions to cause processor 64 toprovide the functionality described herein. Memory 72 may include any ofa variety of solid state, magnetic or optical media, such as RAM, ROM,CD-ROM, magnetic disk, EEPROM, or flash memory.

In the example illustrated by FIG. 5, external defibrillator 12 includesa detection/telemetry interface 76. Detection/telemetry interface 76 mayinclude a port or other physical interface to receive cable 30, which iscoupled to detection device 28, and to electrically couple circuitrywithin defibrillator 12 to circuitry within detection device 28 viacable 30. Cable 30 may include conductors to carry both power and datato and from detection device 28. Alternatively, detection device 28 maybe battery-powered and communicate with external defibrillator 12 bywireless telemetry. Processor 64 communicates with IMD 14 viadetection/telemetry interface 76 and detection device 28.

In some embodiments, as illustrated in FIG. 5, detection/telemetryinterface 76 may convey data between processor 64 and detection device28, as well as provide power from defibrillator 12 to power thecircuitry within detection device 28. As will be described below withreference to FIG. 7, detection device 28 may incorporate wirelesstelemetry circuitry and one or more antennae for communication with IMD14. Detection device 28 may also incorporate a magnet to triggerinitiation of telemetry by IMD 14. In such embodiments,detection/telemetry interface 76 may include any of a variety of knowndigital data interfaces, such as a universal serial bus (USB) interface.In some embodiments, the detection device may not be integrated withtelemetry circuitry. In such embodiments, detection device 28 may beconfigured simply to trigger initiation of telemetry by IMD 14.Telemetry circuitry may be incorporated within defibrillator 12, orthere may be a separate telemetry interface and telemetry head,independent of detection device 28, for providing communication with IMD14.

In other embodiments, external defibrillator 12 may include thetelemetry circuitry, and detection device 28 may include only one ormore antennae for communication with IMD 14. In this case, detectiondevice 28 receives wireless telemetry signals from IMD 14 but transmitsthe received signals to defibrillator for processing. Further, in stillother embodiments, defibrillator 12 may include both telemetry circuitryand antennae for communication with IMD 14. Defibrillator 12 need not becoupled to detection device 28 in order to communicate with IMD 14. Insuch embodiments, detection device 28 may provide wireless communicationwith defibrillator 12, and may be battery powered, e.g., with anon-rechargeable or rechargeable battery, instead of receiving powerfrom defibrillator 12.

FIG. 6 is a flowchart illustrating exemplary operation of externaldefibrillator 12. External defibrillator 12 is brought to patient 16 inresponse to a medical emergency involving patient 16, such as aventricular fibrillation (VF) or sudden cardiac arrest (SCA) experiencedby the patient. A user operates external defibrillator 12, and followsprompts from external defibrillator 12 to visually inspect patient 16 todetermine whether patient 16 has an IMD, and if so, to determine thelocation of the IMD within patient 16. In some embodiments, the user isaided not only by visual or audible prompts, but also detection device28.

In the example of FIG. 6, external defibrillator 12 prompts the user toexamine the patient's chest for a scar near the patient's clavicle (80).As mentioned previously, external defibrillator 12 may include a userinterface that provides a medium for user input indicating whether theuser has found a scar near the patient's clavicle. If the user indicateshe has found such a scar (yes branch of 82), external defibrillator 12prompts the user to place detection device 28 on the patient near thescar (84), so that detection device 28 may initiate communication by IMD14, e.g., by triggering telemetry with a magnet carried by detectiondevice 28.

If the user indicates he does not find such a scar (no branch of 82),external defibrillator 12 prompts the user to examine the patient for araised portion of skin near the patient's clavicle (86). If the userindicates he has found such a raised portion of skin (yes branch of 88),external defibrillator 12 prompts the user to place detection device 28on the patient near the raised portion (90), so that detection device 28may initiate communication by IMD 14. Again, detection device 28 mayintegrate wireless telemetry circuitry for communication with IMD 14, orsimply include a magnet to trigger telemetry by IMD 14.

If the user indicates he does not find such a raised portion of skin (nobranch of 88), external defibrillator 12 prompts the user to placedetection device 28 on the patient near the patient's clavicle (92).External defibrillator 12 may provide other prompts (not shown)prompting the user to move the detection device to various areas of thepatient's chest to use the detection capabilities of the detectiondevice to search for an IMD. For example, the user may swipe detectiondevice 28 across the patient's chest, near the clavicle or elsewhere, toinitiate telemetry by IMD 14. Detection device 28 may include telemetrycircuitry to detect telemetry signals, and thereby detect the presenceof IMD 14. Based on detected signal strength, detection device 28 mayindicate the relative proximity of the detection device 28 to theimplant site of IMD 14. As discussed previously, detection device 28 mayinclude a visible or audible indicator, or both, to indicate thestrength of the telemetry signal, and hence the distance from the IMD14. An indicator, such as an array of lights in which more lights arelit as signal strength becomes stronger, can help the user guidedetection device 28 toward the implant site of IMD 14. In turn, uponplacement of detection device 28 in close proximity to IMD 14, theincreased strength of the telemetry signal will promote more reliabletelemetry with the IMD.

In embodiments in which detection device 28 includes telemetry circuitryfor communicating with IMD 14, detection device 28 placed on thepatient's chest may attempt to establish communication with IMD 14 (94).If communication cannot be established, external defibrillator 12 maycontinue with its typical therapy instructions without communicatingwith an IMD (98). As one example, detection device 28 may be unable toestablish communication because patient 16 does not have an IMD at all.As another example, detection device 28 may be unable to locate an IMDimplanted within patient 16. If communication is established with IMD14, then external defibrillator 12 may coordinate therapy with IMD 14(98), as described in further detail below.

FIG. 7 is a block diagram further illustrating an exemplary detectiondevice 28 of FIG. 1. In the illustrated example, detection device 28includes an antenna 100 coupled to telemetry circuitry 102. Telemetrycircuitry 102 includes a wireless transceiver for RF communication withIMD 14 via antenna 100. Telemetry circuitry 102 may also include variouscircuitry for conditioning signals transmitted or received via antenna100, such as analog to digital and digital to analog converters, andappropriate amplifiers or filters.

A defibrillator interface 104 of detection device 28 interfaces withdetection/telemetry interface 76 (FIG. 5) of external defibrillator 12.Interface 104 may include a plug or other physical interface on cable 30that may be used to removably or permanently couple detection device 28to defibrillator 12, and which electrically couples the circuitry withindetection device 28 to circuitry within defibrillator 12 viadetection/telemetry interface 76. As illustrated in FIG. 7, interface104 may convey data between telemetry circuitry 102 and externaldefibrillator 12, and may receive power from defibrillator 12 fordistribution to the various components of detection device 28. Interface104 may include any of a variety of known digital data interfaces, suchas a universal serial bus (USB) connector. In some embodiments, the USBinterface also may carry operating power for components of detectiondevice 28. In other embodiments, interface 104 may communicate withdefibrillator 12 via a wireless interface, such as an RF or infraredinterface. In these embodiments, defibrillator 12 need not be coupled todetection device 28 in order to communicate with IMD 14. In suchembodiments, detection device 28 may be battery powered instead ofreceiving power from defibrillator 12.

Detection device 28 also includes a magnet 108 to trigger initiation oftelemetry by IMD 14 when detection device 28 is swiped across thepatient's body in proximity to the IMD implant site. Processor 110processes signals received from telemetry circuitry 102, e.g., fortransmission to defibrillator 12 via defibrillator interface 104. Inaddition, processor 110 may measure the signal strength of telemetrysignals received via telemetry circuit 102 in order to drive anindicator 112, such as a visual or audible indicator. As describedabove, indicator serves to indicate the relative proximity of detectiondevice 28 to IMD 14 based on the measured signal strength of telemetrysignals received from the IMD. The signal strength measurement may beperformed for digital signals converted by telemetry circuitry 102.Alternatively, an analog signals strength measurement may be obtained byan analog measurement circuit based on analog signals received bytelemetry circuitry. In either case, the signal strength measurement isused to drive indicator 112.

FIG. 8 is a block diagram illustrating an example detection device 28.In the example of FIG. 8, detection device 28 includes a housing 111, anadhesive layer 112 and a removable backing strip 114. Detection device28 is coupled to external defibrillator 12 by cable 30. Adhesive layer112 may comprise a layer of non-toxic adhesive for adhering detectiondevice 28 to the skin of patient 16. A user may remove removable backinglayer 114 to expose adhesive layer 112, and then attach detection device28 to patient 16. In operation, a bottom surface 115 of detection device28 has a substantially planar surface designed to engage and slideacross the skin of patient 16.

In one embodiment, once a location of IMD 14 within patient 16 has beendetermined, defibrillator 12 may prompt the user to attach detectiondevice 28 to the patient's skin over IMD 14. In particular, the userremoves backing layer 114 to expose adhesive layer 112, and therebypermit adhesive fixation of detection device 28 to the skin of patient16 at the location of the IMD. In this manner, when detection device 28includes telemetry circuitry, detection device 28 remains in proximityto IMD 14 to maintain communication between the two devices, even whenpatient 16 is moved or transported. Adhesive layer 114 thereby promotesreliable and robust communication between defibrillator 12 and IMD 14.In one embodiment, detection device 28 may be a disposable unit that maybe decoupled from cable 30 or defibrillator 12 and discarded after use.

FIG. 9 is a conceptual diagram illustrating an example system 10 thatincludes an external defibrillator 12 communicating with an IMD 14implanted within a patient 16, e.g., via detection device 28 orindependently of detection device 28. IMD 14 may store a variety ofinformation regarding patient 16 and IMD 14 itself within a memory unitof IMD 14 (not shown), and external defibrillator 12 may retrieve thisinformation from IMD 14 during a telemetry session. For example, IMD 14may store demographic information for patient 16, such as name, height,weight, sex, age, residence, date of birth, and the like. Further, IMD14 may store treatment alerts for patient 16, such as medications takenby the patient, allergies of the patient, physician name, physicianphone number, patient's hospital, patient history, patient medicalcondition, patient blood type, or a do not resuscitate (DNR) order forthe patient.

IMD 14 may store information describing the type of IMD 14, pacemaker orinternal defibrillator lead types, ejection fraction, implant lead data,an implant date, lead configuration, lead impedance and currentprogrammed parameters, such as a current pacing mode, pacing amplitude,or defibrillation amplitude. IMD 14 may also store informationidentifying the implant location of IMD 14. When processor 64 ofexternal defibrillator 12 receives such information from IMD 14,processor 64 may store the information in memory 72 as medical eventinformation for patient 16. Such information may then be included in areport of the treatment of patient 16, e.g., a “run” report, along withother medical event information collected by external defibrillator 12as discussed above with reference to FIG. 5. Alternatively, suchinformation may be received directly by a run reporting system from IMD14. Paramedics, first responders, or other users of externaldefibrillator 12 may be required to prepare such run reports by anemergency medical service or other regulating authority. Alternatively,or additionally, such information may be downloaded from the detectiondevice or the run reporting system to a database management system of anemergency room or other location. The information would then beavailable to a physician.

Because external defibrillator 12 may retrieve such patient and deviceinformation from IMD 14 and include the information within the medicalevent information for patient 16 automatically, a user of the externaldefibrillator may not be required to take time to collect suchinformation from patient 16, family members, or bystanders, and enterthe information into external defibrillator 12 manually via userinterface 70 of the defibrillator. Consequently, the user's time andattention may remain focused on treating patient 16. In someembodiments, if external defibrillator 12 is an AED, it may beconfigured to transfer such information to another defibrillator, suchas an ALS defibrillator carried by a paramedic, e.g., by wired orwireless communication, or by physical transfer of a memory card orother data storage medium.

IMD 14 may also store physiological and therapy information. Forexample, IMD 14 may store information relating to current status andhistory of therapy delivery by the IMD to patient 16. Externaldefibrillator 12 may retrieve this stored information from IMD 14, andmay also receive real-time values for one or more physiologicalparameters and real-time indications of therapies delivered or scheduledfor delivery by the IMD from the IMD. For example, externaldefibrillator 12 may receive EGM samples sensed by IMD 14 via leads 26,and may receive a real-time ECG recorded and stored by IMD 14. EGMsignals are a record of changes of cardiac electric potentials, asmeasured with electrodes placed within the heart, either throughcatheters or transvenous leads. Real-time ECG samples may be collectedusing electrodes built into the IMD exterior metal housing. Externaldefibrillator 12 may store any or all of the past or real-timeinformation received from IMD 14 within memory 72.

In addition, external defibrillator 12 may receive informationindicating events or operations within an implanted device, such aspacing, shock or sensing events, all of which may be referred to as IMDevent information. An example of such information is the informationpresented by the Marker Channel™ functionality provided by various IMDsmanufactured by Medtronic, Inc. of Minneapolis, Minn. Such IMD eventinformation can be used by the external defibrillator 12 to interpretoperation of IMD 14. For instance, if the patient is in ventricularfibrillation, a life threatening event, and the patient has a pacemakerthat is delivering pacing pulses, external defibrillator 12 may use theIMD event information obtained from IMD 14 to determine if the pulses itrecords from the electrodes 18 are occurring at the same time as thepaced events indicated by the IMD event information. If so, thenexternal defibrillator 12 can conclude that the IMD 14 is generatingthese events. As another example, external defibrillator 12 may useelectrodes 18 to measure the rate of change of a measured voltage torecognize pacing pulses. In either case, the external defibrillator 12can then analyze periods between the pacing pulses to identifyventricular fibrillation or send a command to the pacemaker to changethe pacing rate to facilitate better interpretation of the patient'sintrinsic rhythm. As a further example, external defibrillator 12 maydetect an impedance signal generated by IMD 14, e.g., changes in tissueimpedance due to pacing pulses by IMD 14. External defibrillator 12 mayuse this information to determine that IMD 14 is present within patient16.

Further, external defibrillator 12 may receive EGM or heart rate datastored by IMD 14, or ECG information obtained via electrodes 18,including average values or other statistical summaries of the heartrate of patient 16 over time. External defibrillator 12 may also receivecurrent heart rate values, or current average heart rate value, e.g.,averaged over a relatively short period of time such as a minute, fromthe IMD. External defibrillator 12 may also receive stored or real-timevalues for other physiological parameters that may be detected by IMD 14as discussed above, such as blood pressure and blood flow. Using thisinformation, external defibrillator 12 can make more informed shockdecisions, and control the timing and parameters of shocks delivered tothe patient by the external defibrillator.

Processor 64 of external defibrillator 12 may provide prompts to a uservia user interface 70, e.g., via speaker 32 and/or display 24, based onthe information received from IMD 14. In some embodiments, providingprompts based on the information received from IMD 14 comprisesmodifying programmed prompts that may have otherwise been provided to auser of defibrillator 12 in the absence of communication with IMD 14.For example, memory 72 of external defibrillator 12 may store visual oraudible prompts provided to a user by processor 64 that indicatelocations for the user to place electrodes 18 on patient 16. If an IMD14 is detected, however, the prompts may be modified to direct the userto place electrodes 18 at locations situated at a distance from the IMDimplant site. For example, the prompts may advise the user to place thedefibrillation electrodes 18 at least six inches (15.24 cm) away fromthe IMD implant site. In this manner, electromagnetic interferencebetween external defibrillator 12 and IMD 14, as well as risk of damageto or reprogramming of IMD 14 caused by defibrillation shock energylevels, may be reduced. Positioning the electrodes 18 further away fromthe IMD 14 may be beneficial to improve the performance of the IMD andexternal defibrillator 12 when both are present and operating together.

As another example, processor 64 may prompt a user of externaldefibrillator 12 with patient treatment alert information received fromIMD 14. For example, processor 64 may provide prompts to the userindicating allergies, potential drug interactions, patient history,patient medical condition, or a DNR order for patient 16. Becausepatient treatment alert information may impact treatment decisions madeby a user of external defibrillator 12, processor 64 may use bold orflashing text, flashing lights, audible alerts, or the like to draw theattention of the user to the presence of one or more patient treatmentalerts.

Additionally, processor 64 may prompt a user with a time of onset of thecurrent medical emergency, or a time elapsed since onset of the medicalemergency, based on the time of onset information received from IMD 14.The efficacy of therapies that could be delivered to the patient mayvary based on the amount of time elapsed since onset of the medicalemergency, e.g., amount of time in fibrillation or SCA. Consequently, auser of external defibrillator 12 may provide different therapies topatient 16 based on the time of onset or amount of time elapsedindicated by external defibrillator 12 based on information receivedfrom IMD 14. For example, a user of external defibrillator 12 may electto deliver defibrillation shocks to patient 16 if the patient has beenin SCA or fibrillation for less than five minutes, and elect to performCPR on the patient if the patient has been in SCA or fibrillation forgreater than five minutes. In some embodiments, external defibrillator12 may prompt the user to provide a particular therapy or type ofmonitoring based on the onset or elapsed time information received fromIMD.

Further, if the received information indicates that IMD 14 is scheduledto deliver a therapy to patient 16, processor 64 may provide a promptnotifying the user of the upcoming delivery of therapy. For example, IMD14 may identify a shockable arrhythmia of heart 22, and transmit anindication to external defibrillator 12 that IMD 14 will deliver adefibrillation shock to the heart. Processor 64 may direct the user toavoid contact with patient, e.g., stop CPR, for a period of time toavoid receiving a portion of the energy of the defibrillation shockdelivered by IMD 14, which may cause discomfort or injury to the user.

Processor 64 may also display some or all of the information receivedfrom IMD 14 via display 24. For example, processor 64 may receive anddisplay the name of patient 16 as stored by IMD 14, allowing a user ofexternal defibrillator 12 to address the patient by name without havingto ask the patient, family members, or other bystanders.

Further, processor 64 may display real-time values of physiologicalparameters sensed by IMD 14, such as a real-time ECG or EGM sensed byIMD 14 via leads 26, via display. Through communication with IMD 14,external defibrillator 12 may be able to display values of physiologicalparameters that may not have otherwise been able to be sensed byexternal defibrillator 12. Processor 64 may provide prompts based onsome of these values. For example, processor 64 may provide audio orvisual prompts regarding the efficacy of CPR provided by a user ofexternal defibrillator 12, e.g., instruction to apply more or lessforceful chest compressions, based on blood pressure or blood flowvalues measured by IMD 14.

EGM waveforms detected by IMD 14 via leads 26 or ECG waveforms may be ofa higher quality than an ECG detected by external defibrillator 12 viaelectrodes 18. For example, an EGM or ECG waveform detected by IMD 14may be less likely to include motion artifacts caused by CPR chestcompressions than an ECG detected by the external defibrillator.Consequently, where available from IMD 14, processor 64 of the externaldefibrillator may display a real-time EGM or ECG waveforms received fromIMD 14. In some embodiments, the processor may select either the ECGdetected by the external defibrillator or ECG or EGM received from theIMD based on criteria related to the quality of the ECGs, such as noiseor impedance. For example, the processor may select the IMD ECG or EGMwhen available unless signal to noise ratio of the external ECG, i.e.,the ECG detected by the external defibrillator, is above a thresholdvalue.

Processor 64 may also display information indicating therapies deliveredto patient 16 by IMD 14 via display 22. Processor 64 may also displayinformation indicating a current status of IMD 14, i.e., what IMD 14 iscurrently doing. If the displayed information indicates that the IMD hasalready delivered therapy to patient 16 in response to the currentmedical emergency, the user may consider such information and therebyavoid delivering redundant therapies to patient 16. For example, thedisplayed information may indicate energy levels of defibrillationshocks delivered to patient by IMD 14, and the user may select an energylevel for a defibrillation shock to be delivered by externaldefibrillator 12 that is adjusted based on the energy levels of thedefibrillation shocks delivered by the IMD. For example, the user mayselect an energy level for a defibrillation shock to be delivered byexternal defibrillator 12 that is greater than the energy levels of thedefibrillation shocks delivered by the IMD if the pulse delivered by theIMD failed to defibrillate heart 22.

External defibrillator 12 may also deliver therapy to patient 16 basedon the information received from IMD 14. For example, in embodiments inwhich processor 64 selects an energy level for a defibrillation shock tobe delivered to patient 16 by external defibrillator 12, processor 64may select the energy level based on the information. The informationreceived from IMD 14 may indicate an energy level of a defibrillationshock delivered to patient 16 by IMD 14, and processor 64 may select anenergy level for a defibrillation shock to be delivered by externaldefibrillator 12 based on the indicated energy level. Processor 64 mayselect a higher energy level to avoid delivering a redundantdefibrillation shock which may have already proven ineffective at endingfibrillation of heart 22.

As another example, in embodiments in which processor 64 analyzes an ECGto determine whether to deliver therapy, e.g., a defibrillation shock,to patient 16, processor 64 may analyze a real-time ECG received fromIMD 14. As discussed above, the ECG or EGM received from IMD 14 may beof a higher quality, e.g., less susceptible to motion artifacts from CPRchest compressions, than an ECG detected via electrodes 18.Consequently, by using an ECG or EGM received from IMD 14, processor 64may be able to more accurately determine whether therapy should bedelivered to patient 16. Additionally, as discussed above, processor 64may select one of the IMD and external ECG for analysis based on acriterion related to the quality of at least one of the ECGs, therebysupporting coordinated operation of external defibrillator 12 and IMD14.

Further, in some embodiments, IMD 14 may use different algorithms todetermine whether to deliver therapy to patient 16 than are available toprocessor 64, and processor 64 may deliver therapy based on a therapydelivery decision received from IMD 14. For example, IMD 14 may applyarrhythmia detection algorithms to the rhythm of heart 22 thatdistinguish between ventricular and supra-ventricular arrhythmias. IMD14 may decide that a defibrillation shock should be delivered inresponse to detection of a ventricular arrhythmia, and that adefibrillation shock should not be delivered in response to detection ofa supra-ventricular arrhythmia. Processor 64 may control delivery of adefibrillation shock to patient 16 based on a defibrillation shockdelivery decision received from IMD 14. In this manner, externaldefibrillator 12 may, for example, avoid delivering a defibrillationshock to treat a supra-ventricular arrhythmia. In some embodiments, auser may override a decision by processor 64 not to deliver therapybased on information received from IMD 14, and direct defibrillator 12to deliver therapy.

Additionally, processor 64 may control delivery of therapy by externaldefibrillator 12, e.g., control charging circuit 66 and therapy deliveryinterface 60, based on onset or elapsed time information received fromIMD 14. For example, processor 64 may select a therapy, such asdefibrillation, cardioversion or pacing, or the energy levels for suchtherapy, based on the time. Processor 64 may alternatively suspenddelivery of therapy by external defibrillator 12 based on the timeinformation.

Processor 64 of external defibrillator 12 may also control delivery oftherapy by IMD 14. For example, processor 64 may suspend delivery oftherapy by IMD 14 during treatment of patient 16 with externaldefibrillator 12. By suspending delivery of therapy by IMD 14, externaldefibrillator 12 may avoid interference between therapies delivered byIMD 14 and defibrillator 12. As another example, external defibrillator12 may deliver therapy upon receiving information from IMD 14 that IMD14 has a low battery, or that IMD 14 has delivered a maximum number ofshocks.

As another example, processor 64 may change a therapy delivery mode ofIMD 14. For example, after defibrillation by external defibrillator 12,some patients may benefit from pacing in a different mode than the modein which IMD 14 had been programmed. Processor 64 may change the mode ofIMD 14 by, for example, changing IMD 14 from single to dual chamberpacing or from demand to non-demand pacing, or by changing a pacing rateor the aggressiveness of rate responsive pacing or by increasing pacingamplitudes.

Further, the hearts of some patients are left in a state of pulselesselectrical activity after being defibrillated. Such patients may benefitfrom delivery of post extra-systolic potentiation (PESP) pacing, whichmay increase the cardiac output of their heart. If IMD 14 is capable ofdelivering post extra-systolic pacing pulses, processor 64 may directIMD 14 to do so after heart 22 has been defibrillated. In someembodiments, processor 64 may direct IMD 14 to delivery other therapiesprovided by the IMD that may not be available from the externaldefibrillator, such as cardioversion or anti-tachycardia pacingtherapies or by increasing pacing amplitudes, after the shock wasdelivered by the AED.

Additionally, processor 64 may direct IMD 14 to deliver therapy that iscoordinated with therapy delivered by defibrillator 12. For example,processor 64 may direct IMD 14 to deliver a defibrillation shocksynchronized with, or with some other temporal relationship to, adefibrillation shock delivered by defibrillator 12. Delivery ofdefibrillation shocks by both IMD 14 and external defibrillator 12 maybe more efficacious than delivery of defibrillation shocks by either theexternal defibrillator or the IMD alone.

As another example, external defibrillator 12 may include pacingcircuitry for delivery of pacing pulses to heart 22 of patient 16 viaelectrodes 18. To the extent IMD 14 is not capable of delivering postextra-systolic pacing pulses, processor 64 may control the pacingcircuitry to deliver pacing pulses an extra-systolic interval afterdelivery of a pacing pulse by IMD 14, or an intrinsic depolarization ofheart 22. Processor 64 of external defibrillator 12 may interrogate IMD14 to identify the therapies sensing capabilities provided by the IMD.Processor 64 may control the IMD to deliver a therapy alone, or incoordination with the external defibrillator, based on this capabilityinformation retrieved from the IMD.

As described above, processor 64 collects medical event informationduring treatment of patient 16 with external defibrillator 12, andstores the medical event information within memory 72 of the externaldefibrillator. Processor 64 may also store the medical event informationinto IMD 14. In this manner, caregivers who subsequently treat patient16 and have access to a programming device that communicates with IMD 14may be able to retrieve the medical event information. In the absence ofcommunication between IMD 14 and external defibrillator 12, suchcaregivers may not have had access or timely access to the medical eventinformation, which may inform treatment decisions made by thecaregivers, and may supplement the medical records maintained forpatient 16 by the caregivers. In some embodiments, rather than acaregiver retrieving the information with a programming device, IMD 14may transmit the medical event information to a computing device,computing network, or other data repository at, for example, a hospital.The medical event information may supplement the hospitals records forthe patient, and may be available to caregivers throughout the hospitalwho may treat the patient.

Various embodiments of the invention have been described. However, oneskilled in the art will appreciate that various modifications may bemade to the described embodiment without departing from the scope of theclaimed invention. For example, although wireless communication has beendescribed herein primarily in the context of RF telemetry, the inventionis not so limited. An external defibrillator and IMD according to theinvention may include any of a variety of RF, optical, acoustic, orother transducers for wireless communication. Further, althoughdescribed in the context of communication with an IMD, an externaldefibrillator according to the invention may communicate with otherexternal medical devices that are associated with the patient, such as awearable defibrillator or Holter monitor. In addition, althoughdescribed in the context of an external defibrillator, the IMD may beany implantable device, such as a neurostimulator, a drug pump, or adiabetes monitoring device. These and other embodiments are within thescope of the following claims.

1. An external defibrillator comprising: a defibrillation therapy generator; electrodes coupled to the defibrillation therapy generator; and a user interface that presents one or more prompts to a user of the external defibrillator to detect presence of an implantable medical device (IMD) in a patient.
 2. The external defibrillator of claim 1, wherein the user interface presents a prompt requesting that the user examine an area of the body of the patient for evidence of presence of an IMD in the patient.
 3. The external defibrillator of claim 1, wherein the user interface presents: a first prompt requesting that the user examine a chest of the patient for a scar near clavicles of the patient; a second prompt requesting that the user examine the chest of the patient for a raised portion of skin near the clavicles of the patient; a third prompt requesting that the user place a detection device on the chest of the patient near the clavicles of the patient; and a fourth prompt requesting that the user place the electrodes on the patient's chest based on the location of the IMD.
 4. The external defibrillator of claim 1, wherein the prompts include at least one of audible prompts or visual prompts, the external defibrillator including a device to present at least one of the audible prompts or visual prompts.
 5. The external defibrillator of claim 1, wherein the user interface provides a medium for user input indicating that the user has detected presence of the IMD.
 6. The external defibrillator of claim 1, further comprising a detection device that detects presence of the IMD, wherein the detection device is configured to trigger initiation of telemetry by the IMD and detect the presence of the IMD based on reception of one or more telemetry signals from the IMD.
 7. The external defibrillator of claim 6, further comprising a processor that receives information from the IMD via the telemetry signals, wherein the processor controls the therapy generator to deliver therapy to the patient based on the received information.
 8. The external defibrillator of claim 7, wherein the received information includes electrogram information, electrocardiogram information, and IMD event information.
 9. A method comprising generating one or more prompts to a user of an external defibrillator to detect presence of an implantable medical device (IMD) in a patient.
 10. The method of claim 9, further comprising presenting a prompt requesting that the user examine an area of the body of the patient for evidence of presence of the IMD in the patient.
 11. The method of claim 9, further comprising generating: a first prompt requesting that the user examine a chest of the patient for a scar near clavicles of the patient; a second prompt requesting that the user examine the chest of the patient for a raised portion of skin near the clavicles of the patient; a third prompt requesting that the user place a detection device of the external defibrillator on the chest of the patient near the clavicles of the patient; and a fourth prompt requesting that the user place electrodes of the external defibrillator on the patient's chest based on the location of the IMD.
 12. The method of claim 9, wherein generating one or more prompts includes generating at least one of audible prompts or visual prompts.
 13. The method of claim 9, wherein detecting presence of an IMD in the patient comprises triggering initiation of telemetry by the IMD and detecting the presence of the IMD based on reception of one or more telemetry signals from the IMD.
 14. The method of claim 13, further comprising: receiving information from the IMD via the telemetry signals; and delivering therapy to the patient based on the received information.
 15. The method of claim 14, wherein the received information includes electrogram information, electrocardiogram information, and IMD event information. 